Friction is known as the resistance to motion of one object moving relative to another. According to scientists it is the result of the electromagnetic attraction between charged particles in two touching surfaces.

1. By Prof. Liwayway Memije-Cruz

2.  a force that
holds back the
movement of
a sliding
object.

5. If a car needs to stop at a
stop sign, it slows
because of the friction
between the brakes and
the wheels.

6. If you run down the street and
stop quickly, you can stop
because of the friction between
your shoes and the cement.

8. Friction is still there, but the liquid
makes the surfaces smoother and
the friction a lot less. Less friction
means it is harder to stop.

9.  is the friction that builds up between the tires on a
car and the pavement.
 Rolling traction is the interaction between the tire
and the surface, which results in forward motion.
When water coats that surface, the tire can't obtain
traction.

10. The low friction thing happens to
cars when it rains. That's why
there are often so many
accidents. Even though the
friction of the brakes is still there,
the brakes may be wet, and the
wheels are not in as much
contact with the ground.

12.  Hydroplaning occurs when your tires move over a wet surface so quickly that
they don't have time to displace enough water and contact the surface. The
water lifts the tire up from the surface, and the vehicle begins to hydroplane.
 While speed, road conditions and tire wear all play a part, the main cause of
hydroplaning is water depth.
 Hydroplaning is possible whenever water accumulates to a depth of one-tenth
of an inch (0.3 centimeters) or more for at least 30 feet (9.14 meters) and a
vehicle moves through it at 50 miles per hour (22.35 meters per hour) or more
Tire size and tread patterns are also important. Hydroplaning is more likely to
happen if your vehicle has narrow tires. Worn tires are more dangerous in wet
conditions. Certain tire tread patterns are better at channeling water away
than others. All wheel driven vehicles are more likely to hydroplane than two-
wheel drive vehicles, because their computerized differentials may shift power
from the front to the rear tires, creating a hydroplaning situation. Heavy
vehicles are less prone to hydroplaning.

13.  Friction is the reason humans are able to control where they
move or why objects can stay in one place, but it is also the
reason we must use force and lose energy to move objects and
why many materials wear out and break.
 The reality of friction allows machines to work, humans to walk
and cars to drive.
 Friction also means that energy needs to constantly be exerted
to move any object.
 When two surfaces are in contact, friction stops those surfaces
from sliding against each other. All machines make use of
friction and without it would have no use.

14. Without friction we are handicap.
1. It is becomes difficult to walk on a slippery road due to low
friction. When we move on ice, it becomes difficult to walk
due to low friction of ice.
2. We can not fix nail in the wood or wall if there is no friction.
It is friction which holds the nail.
3. A horse can not pull a cart unless friction furnishes him a
secure Foothold.

15.  it makes moving large objects extremely difficult and causes
surfaces to wear and break.
 it is a physical constraint, but also makes controlled movement
and work possible.
 produces heat in various parts of machines. In this way some
useful energy is wasted as heat energy.
 Due to friction we have to exert more power in machines.
 It opposes the motion.
 Due to friction, noise is also produced in machines.
 Due to friction, engines of automobiles consume more fuel which
is a money loss.

18. The parts of machines which are
moving over one another must be
properly lubricated by using oils
and lubricants of suitable
viscosity.

19. Proper greasing between the
sliding parts of machine reduces
the friction

20. In machines where possible,
sliding friction can be replaced by
rolling friction by using ball
bearings.

22. * Sliding Friction, also known as kinetic
friction, takes place when an object
slides over another.
* The aim of sliding friction is to stop an
object unlike rolling friction. It acts
between objects already in motion.
* Kinetic friction is caused by chemical
bonding between surfaces rather than
interlocking between them.

23.  Fk = Uk N
 Where,
F = Sliding or kinetic
friction
Uk= Coefficient of sliding
friction
N = Normal reaction due
to weight

24. When two objects are not moving
relative to each other, a force
opposes or resists the lateral
movement of the objects.

25.  Fs= Fmax = UsN
 Example: When wepush a
heavy object and areunableto do
so, wepush it harder and harder,
after sometimeit moves
suddenly and after itsmovement
it'seasier to push it.
Here:
1. Becauseof Static friction we
wereunableto movetheobject.
2. When it moved, we had
overcomethekinetic friction
which waslessthen static
friction. If thecoefficient of
static friction ishigh, it means, a
lot of forcewill berequired to
overcomethisstatic condition of
theobject and to get it in motion.

26. occurswhen an object rolls
over asurface.
actson thepoint of the
contact of therolling object
and thesurfaceon which it is
rolling.
tendsto slow down the
rolling motion of theobject.
thecombination of various
other forces.

27.  Deformation of the object
 Deformation of the surface
 The diameter of the wheels
surface
 The movement below the
surface
 Sliding
 Surface adhesion
 Surface properties
 Material of the object
 Temperature

28.  When we ride our bike
through soft dirt, it is
difficult to do so because
rolling friction comes into
action and hence opposes
motion. It is very interesting
to note that it is easier to
drive through soft dirt if the
tire also has less air, this is
because the traction is
increased which leads to
improved driving.

29.  F = Crr N
 Where,
F = force of friction
Crr= coefficient of rolling
friction
N or W = weight of the
object (wheel) in this case
 (1) Rolling resistance is not
directly dependent on the
weight of the vehicle as
obvious in the above
equation.
(2) When we apply brakes to
any moving vehicle, rolling
friction changes to kinetic
sliding friction.

30.  http://physics.tutorvista.com/forces/types-of-friction.html
 http://byjus.com/physics/rolling-friction/
 http://www.physics4kids.com/files/motion_friction.html
 http://study.com/academy/lesson/friction-definition-and-types.html